Sheilding gas mixtures.

Date 10-14-2010 20:31

I am welding GMAW process and using a 90% argon/10% CO2 mix. The CoC for the wire that I have chosen which is Lincoln E70C-6M-H8 says that it tested with 75% argon/25% CO2. Can I use the 90/10 gas mixture? When writing a WPS for this process can I write in the gas mix information as 75% argon/ 25% CO2 +/- 15%?

By js55

Date 10-15-2010 10:30

You didn't say what code.
But in general the answers are:
Yes.
Depends.

By Lawrence (*****)

Date 10-16-2010 04:36

Brow

If you want spray transfer your going to have to use a gas with at least 80% Argon.

The manufacturers data sheet only stated that their published mechaicals were done using 75/25

As far as D1 goes your 90/10 is a legit spray gas...

By 877412

Date 10-15-2010 04:53

Interesting question.
D1.1-2010 Table 3.8 says that a change in the "nominal" composition of shielding gas is an essential variable----but dosen't define "nominal".
Perhaps looking in AWS 5.32 or A5 specification would shed more light on the official definition.

OPINION:
I have seen others use that approach you had mentioned and I never knew if it was totally acceptable nor did I like it
as that would mean you could go down to 60% argon and 40% CO2 as well as up to 90/10.
So I would have stayed with the 90/10%

Regarding the company specification being listed as 75/25 only indicates that they had tested that specific filler with that shield gas combination and got the best mechanical results so they can put that in their sales spefications info. MY assumption --right or wrong is that they had also tested with other combinations and did not reach the same or less mechanical specifications so they only listed the best that they had achieved. Call the manufacturer and ask the question!

Fact:
I would use the 90/10 as that is the gas you are in fact using and that is what should be listed on the WPS.
If you are doing a PQR tensile I have know that a good tensile only has to meet the minimum tensile of the base metal and the fillers are always stronger than the base as fillers are listed as minimums by manufacturers and following AWS specifications .
I have almost always found those mfg. specs. to be stronger than the minimum.

K Karwowski
IE E70C would have to show a manufacturers spec for the min. of 70K but the actual printed and proven specs are almost always above the min.

By browland (*)

Date 10-15-2010 11:47

Thanks for the input.
I am trying to write the WPS to D1.1 code. The other factor that I have encountered is that I want to use this same WPS for E70S-6 wire too and on that .035 wire we like the 75%/ 25% arg/CO2. This is why I would like to know and incorporate any variables allowed by AWS when describing gas mixtures.

If I can do this it will give me more coverage on a single WPS, this way I don't need to have so many WPS's!

By fschweighardt (***)

Date 10-15-2010 15:05 Edited 10-15-2010 15:09

AWS D1.1 2010 3.7.4 say you shall use A 5.32 gas. A5.32 says you are allowed +/-10% of the minor component as a range before the gas falls into another classification. The nominal composition is 25% CO2, the min/max is 22.5% to 27.5%. If your gas is outside those ranges it either needs to be considered:
out of spec and not usable for this WPS
or another classification, and labeled as such which would be a change in nominal composition

3.7.4 says that in addition to the above, the gas in the procedure must be either the gas used for A5.XX specification or a gas that is recommended for use by the manufacturer. If the gas is recommended and is not the standard gas used in the A5.XX for that wire, the recommendation shall be supported by test results as required by the applicable A5.XX document

By Lawrence (*****)

Date 10-16-2010 04:40

If your running 75%/ 25% arg/CO2 with your .035 solid wire you are not running spray transfer... Keep in mind that short circuiting transfer (not pre-qualified) requires procedures that are qualified by testing.

Its easy enough to write WPS for both solid wire and MCAW if you stay in pre-qualified status.